# A car manufacturer is comparing two fuels for use in a new engine: petrol and liquefied petroleum gas (LPG), which is mainly propane. Explain the advantages and disadvantages of using LPG instead of petrol as a fuel for cars.

> OCR A-Level Chemistry B: Salters (H433) — DF Developing fuels · Explain · 5 marks

> Petrol is a liquid fuel obtained from crude oil and is widely used in car engines. LPG (liquefied petroleum gas) is also obtained from crude oil but contains shorter-chain hydrocarbons such as propane. Both fuels release energy by combustion.

## Mark scheme (5 marks)

1. Complete combustion of LPG/propane produces carbon dioxide and water only, so fewer toxic pollutants such as carbon monoxide are produced compared to petrol
2. LPG produces fewer particulates / less soot than petrol because the hydrocarbon chains are shorter
3. LPG is still a non-renewable fossil fuel / it will eventually run out, so it is not a long-term sustainable solution
4. LPG must be stored under pressure as a liquid, which requires a stronger/heavier fuel tank, making it less convenient than petrol
5. LPG still releases carbon dioxide when burned, contributing to the greenhouse effect / climate change, so it does not eliminate the problem of global warming

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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